Government plans for immigration after Brexit have been thrown into chaos after immigration minister Brandon Lewis contradicted earlier indications that free movement would continue after March 2019.

Insisting that Britain would no longer adhere to the free movement of people – one of the EU’s four freedoms – when it leaves the bloc in spring 2019, Mr Lewis said the UK would have a new immigration system in place in just 20 months’ time.

“There will be a new immigration system in place from the spring of 2019 and that will be outlined in the Immigration Bill that will go through Parliament next year,” he vowed.

But Mr Lewis told BBC Radio 4’s Today programme: “Free movement of labour ends when we leave the European Union in the spring of 2019 – we’re very clear about that.”

Asked why free trade and single market access would not also end then, Mr Lewis said: “There’s a period of negotiation we’re going through with the European Union at the moment, but we’re very clear that free movement ends – it’s part of the core principles, the four key principles, of the European Union – when we leave.”

Pressed on whether it was a red line to end free movement in March 2019, he said: “It’s a simple matter of fact that the four key principles of the European Union include free movement – we won’t be a member of the European Union when we leave.”

In the interview the immigration minister also repeatedly failed to say whether the Conservatives would achieve their manifesto pledge to bring migration down to the tens of thousands by the end of this Parliament, in 2022.

Asked several times on Radio 4 whether his department would achieve its manifesto commitment, he replied: “It’s not a straight-forward issue. We cannot control our net migration levels fully until we leave the European Union.”

The latest statistics show that net long-term migration for EU citizens – the balance between arrivals and departures – was running at an estimated 133,000 last year, a fall of more than a quarter on 2015. But, overall international net migration, including from outside the EU, stood at 248,000 in 2016 – considerably above the Government’s target.

Diane Abbott, the Shadow Home Secretary, said: “There is far too much heat and not enough light about immigration, so any truly objective and well-informed analysis must be welcome.

”We already know that immigrants, both EU and non-EU, make a huge contribution to the economy and to wider society. They occupy both high-skilled, high-wage jobs and lower-skilled, lower-paid ones, adding value across a wide range of economic sectors. They help make the UK more internationally competitive, and sectors with staff shortages, such as the NHS, social care and agriculture, would be in serious difficulty without them.

“The report should be published. There must be no repeat of the buried Home Office reports into international students, or the Saudi funding of terrorism. And there should be no attempt to reform the immigration system until the report has been published and debated.”